IAC Red Set Science Bee Practice Test

The main idea here is where the electron transport chain operates and why Coenzyme Q10 is tied to a key step in energy production. The Q cycle is part of the electron transport chain and runs in the inner mitochondrial membrane. Coenzyme Q10, also called ubiquinone, acts as a mobile electron carrier that shuttles electrons between Complexes I or II and Complex III. Within Complex III, the Q cycle uses these electrons to move them along to cytochrome c while pumping protons across the membrane, building the proton gradient that powers ATP synthesis. All of this energy-producing machinery sits in the mitochondria, which is why they’re nicknamed the powerhouse of the cell. The nucleus, ribosome, and lysosome perform other essential cellular roles and do not host the main energy-generating chain.